Building encasement elements are used, in a known way, in foil roof systems and foil facade systems. These foil roof and foil facade systems are advantageously used in erecting commercial buildings, such as sports stadiums, convention centers, or shopping centers. These buildings that usually have very large roof and facade surface areas utilize, among other things, the advantages associated with foil roof or foil facade systems, such as lightness and transparency or flexibility of the coloring.
According to standards, foil cushions are made from two outer foil layers that are connected to each other in an essentially fluid-tight way and that are commonly welded to each other along their edges, in order to form an essentially fluid-tight, enclosed hollow space between the layers. During the production of the foil cushion, a fluid medium, in particular, a gas, such as, e.g., air, is introduced into this hollow space, by means of which the foil layers are tensioned accordingly and the foil cushion obtains its intended shape. In the installed state, the foil cushions are also usually equipped with a device for supplying a fluid medium. This device can regulate, for example, the air pressure in the foil cushion.
The fluid medium introduced into the foil cushion, however, is used not only for shaping the cushion, but also for thermal insulation, which forms another advantage of the foil system.
In order to withstand intense stresses on a building envelope, such as, for example, wind loads, and here, in particular, wind-drag loads, existing solutions propose to double the outer foil layer. Through this doubling, a foil cushion can absorb higher stresses, in particular, wind-drag loads. A disadvantage here, however, is primarily the high material use that can lead to high costs for large surface area building envelopes. Although the two outer foil layers are connected to each other in an essentially fluid-tight way, it definitely often happens that condensate forms between these two foil layers, which is undesirable just for visual reasons.
Therefore, one problem of the present invention is to improve a building encasement element of the type named above such that at least one of the mentioned disadvantages is lessened.